Problem: What is the sum of all of the solutions of the equation $\frac{4x}{20}=\frac{5}{x}$?
Explanation: Rewrite $\frac{4}{20}$ as $\frac{1}{5}$ and multiply both sides by $5x$ to obtain $x^2=25$.  The solutions of this equation are $\pm\sqrt{25}=\pm5$, and their sum is $(-5)+5=\boxed{0}$.